December 2025 Q&A
Q: Can I ground through a wave trap?
A: General discussion about wave or line traps centers on their function. At operating frequency, they have extremely low impedance to any voltage at 60 Hz. Some would say that for the sake of convenience, it’s OK to ground at a switch even where there is a line trap on its load side. That is a bit too simplified. Historically, we isolated a transmission line and grounded it to protect the crew. Sometimes a trap would be situated between the ground point and the work location. Today, we don’t ground to protect workers; we bond to protect them and ground to isolate the source.
Most traps have both a surge suppressor and a capacitor parallel with the trap circuit. Does that affect sudden current rise on the grounded circuit? It might, but that depends on existing conditions and what caused the fault current. We create typical ground paths that are expected to be as resistance-free and reliable as possible to accomplish the task (i.e., tripping the circuit). Any circuit elements that might compromise ground path performance should be eliminated, which is accomplished by bonding across the wave trap to ensure a reliable, resistance-free ground path. However, if we examine what we are attempting to accomplish, doing so may not be that important.
Many current opinions are based on misapplied grounding policy, so let’s start there. The purpose of grounding in a substation is to trip the protective devices of an offending circuit. It is the arrangement of the grounding connections to create an equipotential environment that protects the worker. If our bonding arrangement on the field side of the wave trap is effective, the worker will be protected. The grounding of the circuit in the work area passing through the wave trap, just like any ground fault on the circuit, should not be much of an issue. The low impedance will pass the current necessary to cause a trip of the circuit protectors. We think most readers would agree that it is still a good idea to place sufficient grounds at the load side of the open switch in the substation.
Any personnel protected by a transmission ground is in an equipotential zone, meaning near the worker, with much less likelihood of a trap in the pathway. Remember, since the ground scheme requires short-circuiting phases one, two and three, that short-circuiting – as well as any ground – will do its part to trip the circuit while the bonding connection protects the worker.
Q: In an underground transformer, my understanding is that the neutral or concentric neutral should be treated as a potential source when it places a worker in the minimum approach distance. I have always struggled to address bonded neutrals when explaining this concept to lineworkers who have worked them uncovered for years. Can you help?
A: First, we must understand the nature of the overhead system neutral and minimum approach distance, which is not a simple task. MAD includes two modes of protection for the worker. Per OSHA 29 CFR 1910.269(l)(3)(iii)(B), the “employer shall ensure that no employee approaches or takes any conductive object closer to exposed energized parts than the employer’s established minimum approach distance, unless the energized part is insulated from the employee and any other conductive object at a different potential.” This rule has an important difference from insulating the worker, as described in 1910.269(l)(3)(iii)(A). Paragraph (l)(3)(iii)(B) is conditional, requiring the energized part to be insulated from any other potential, including ground. The rule appears to be constructed largely around worker exposure to higher voltages within the vicinity of a neutral while handling conductive objects, especially unfixed objects like jumpers or moving phases. It also applies where a worker’s exposure could be between an energized phase and path to ground, including poles, hardware and crossarms. To comply with (l)(3)(iii)(B), if you are within the MAD of a distribution phase, you must cover the neutral or maintain the primary MAD from it.
It makes sense, then, that per (l)(3)(iii)(A), if the worker is insulated from contact, the MAD for the exposure voltage applies to each level of exposure. Since the voltage of a grounded system neutral is near zero, the “avoid contact” rule from 1910.269’s Table R-6 applies, provided you are outside the MAD for any other exposure.
But we’re not done yet. The question now is, will you be in contact with the system neutral? If so, we must accommodate all conditions of exposure, including a fault condition. Additionally, depending on the grounding and bonding of the neutral, a voltage exposure could exist based on the principle of potential difference. Electrical insulation (i.e., either gloves or coverup) is required where a difference is present. These same exposure conditions apply to insulated URD.
OSHA defines “insulation” as insulating cover rated for the voltage involved. However, we know from experience that URD primary insulation is not universally trustworthy.
When the primary is insulated, properly bonded bare neutrals do not create primary exposure and thus are not treated with primary MADs. Neutrals are grounded and bonded to the enclosure so that the voltage is lower than secondary, meeting the requirements of “avoid contact.” However, the potential between a primary neutral and any ground potential could be lethal under fault conditions or if bonding is poor or nonexistent.
A visual inspection can provide relative confidence that the elbow is safe and insulation for the voltage MAD does not apply. We also know that as an industry rule, we don’t handle elbows with rubber gloves or contact them in any way except with rated sticks. While we have historically treated an uninsulated concentric neutral differently, it is no different than an overhead system neutral.
Covering the elbow with a blanket is one more step toward safety that can be performed with rubber gloves. While this approach is not required, it is permitted under the rules for insulated facilities. Neutrals in pad-mounts should always be handled with rubber gloves. Many employers allow Class 0 for URD neutrals; we suggest Class 2.
Q: Do you have any updates about infrastructure resilience planning? A group of us who work for a small cooperative recently attended a meeting with state officials who asked what’s being done to harden systems due to climate change pressures. We heard a few speakers say that state regulatory actions were forthcoming, particularly regarding storm response plans. I know OSHA requires emergency actions plans, but which agencies require storm response plans? Does FERC or NERC require them?
A: In 2016, the U.S. Department of Energy published a guide titled “Climate Change and the Electricity Sector.” The agency assembled a group of about a dozen utility stakeholders representing municipal employers, investor-owned utilities and cooperatives, with the goal of establishing an approach to future aspects of environmental change. Only a few utilities established a plan, finding it challenging to set goals in the face of a substantial amount of contradictory information.
While utilities may be keeping an ear to the ground regarding the environment, it appears they are still basing their infrastructure growth primarily on predictions, the economy and maintenance of their aging systems. Few utilities can say that there has been a trend of system disturbance related to unusual climate events that did not occur in previous decades, so the urgency seems to be lacking in some respects. Interconnecting grids and microgrids has helped establish reliability as structure technologies are hardened for various reasons, most of which are not related to climate change. Few industry professionals will agree that there is one primary reason for setting these goals.
Each U.S. state has its own version of a public service commission, which is required to carry out various duties. Some commissions, like the one in Texas, mandate emergency action plan filings. Many requirements are related to National Incident Management System coordination.
FERC/NERC Critical Infrastructure Protection (CIP) authorities focus on cyber and physical safety and reliability, particularly with large and bulk suppliers that require incident reports and action plans related to NERC goals. To achieve these goals, many utilities have various levels of CIPs depending on their interconnected transmission and generation infrastructures.
Do you have a question regarding best practices, work procedures or other utility safety-related topics? If so, please send your inquiries directly to kwade@utilitybusinessmedia.com. Questions submitted are reviewed and answered by the iP editorial advisory board and other subject matter experts.